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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var num = 10;
        console.log(typeof num); //number
        var str = 'pink'; 
        console.log(typeof str);//string
        var flag = true;
        console.log(typeof flag); // boolean
        var vari = undefined;
        console.log(typeof vari); //undefinded
        var timer = null;
        console.log(typeof timer); //object
        // prompt 取过来的值是 字符型的
        var age = prompt('请输入您的年龄');
        console.log(age); 
        console.log(typeof age);
    </script>
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